The formation of nanocrystalline orthoferrites of rare-earth elements XFeO3 (X = Y, La, Gd) via heat treatment of coprecipitated hydroxides

Resumo

Heat treatment of coprecipitated hydroxides in air has afforded isometric nanocrystals of rhombic yttrium, lanthanum, and gadolinium ferrites with average crystallite size 40±4 nm. It has been stated that the formation of XFeO₃ (X = Y, La, Gd) nanocrystals occurs via two mechanisms, from the corresponding coprecipitated hydroxide (main route) and from the products of partial carbonatization of the precursor (side route). It has been shown that the formation of XFeO₃ (X = Y, La, Gd) nanocrystals via the main and the side routes occurs at 500 and 780°С (o-YFeO₃), 646 and 900°С (o-LaFeO₃), and at 769°С (o-GdFeO₃). Basing on the obtained data, we have suggested a scheme of chemical and physical transformations accompanying the formation of nanocrystals of yttrium, lanthanum, and gadolinium ferrites.